nfd-master: add DisableAutoPrefix feature gate

Now that we have support for feature gates deprecate the autoDefaultNs
config option of nfd-master and replace it with a new alpha feature gate
DisableAutoPrefix (defaults to false). Using a feature gate to handle
and communicate these kind of changes, where the default behavior is
intended to be changed in a future release, feels much more natural than
using random flags/options.

The combined logic of the feature gate and the config option is a
logical OR over disabling auto-prefixing. That is, auto-prefixing is
disabled if either the feature gate or the config options is used set to
disable it:

                       | DisableAutoPrefix (feature gate)
                       | false | true
  -------------------- | --------------------------------
  autoDefaultNs   true |  ON   | OFF
  (config opt)   false |  OFF  | OFF

docs/reference/feature-gates.md

@@ -16,7 +16,8 @@ The feature gates are set using the `-feature-gates` command line flag or
 
 | Name                  | Default | Stage  | Since   | Until  |
 | --------------------- | ------- | ------ | ------- | ------ |
-| `NodeFeatureAPI`      | true    | Beta   | V0.14   |   |
+| `NodeFeatureAPI`      | true    | Beta   | V0.14   |        |
+| `DisableAutoPrefix`   | false   | Alpha  | V0.16   |        |
 
 ## NodeFeatureAPI
 
@@ -25,3 +26,27 @@ When enabled, NFD will register the Node Feature API with the Kubernetes API
 server. The Node Feature API is used to expose node-specific hardware and
 software features to the Kubernetes scheduler. The Node Feature API is a beta
 feature and is enabled by default.
+
+## DisableAutoPrefix
+
+The `DisableAutoPrefix` feature gate controls the automatic prefixing of names.
+When enabled nfd-master does not automatically add the default
+`feature.node.kubernetes.io/` prefix to unprefixed labels, annotations and
+extended resources. Automatic prefixing is the default behavior in NFD v0.16
+and earlier.
+
+Note that enabling the feature gate effectively causes unprefixed names to be
+filtered out as NFD does not allow unprefixed names of labels, annotations or
+extended resources. For example, with the `DisableAutoPrefix` feature gate set
+to `false`, a NodeFeatureRule with
+
+```yaml
+  labels:
+    foo: bar
+```
+
+will turn into `feature.node.kubernetes.io/foo=bar` node label. With
+`DisableAutoPrefix` set to `true`, no prefix is added and the label will be
+filtered out.
+
+Note that taint keys are not affected by this feature gate.

docs/reference/master-configuration-reference.md

@@ -70,6 +70,9 @@ denyLabelNs: ["denied.ns.io","denied.kubernetes.io"]
 
 ## autoDefaultNs
 
+**DEPRECATED**: Will be removed in NFD v0.17. Use the
+[DisableAutoPrefix](feature-gates.md#disableautoprefix) feature gate instead.
+
 The `autoDefaultNs` option controls the automatic prefixing of names. When set
 to true (the default in NFD version {{ site.version }}) nfd-master
 automatically adds the default `feature.node.kubernetes.io/` prefix to

pkg/features/features.go

@@ -21,7 +21,8 @@ import (
 )
 
 const (
-	NodeFeatureAPI featuregate.Feature = "NodeFeatureAPI"
+	NodeFeatureAPI    featuregate.Feature = "NodeFeatureAPI"
+	DisableAutoPrefix featuregate.Feature = "DisableAutoPrefix"
 )
 
 var (
@@ -33,5 +34,6 @@ var (
 )
 
 var DefaultNFDFeatureGates = map[featuregate.Feature]featuregate.FeatureSpec{
-	NodeFeatureAPI: {Default: true, PreRelease: featuregate.Beta},
+	NodeFeatureAPI:    {Default: true, PreRelease: featuregate.Beta},
+	DisableAutoPrefix: {Default: false, PreRelease: featuregate.Alpha},
 }

pkg/nfd-master/nfd-master-internal_test.go

@@ -333,6 +333,10 @@ func TestRemovingExtResources(t *testing.T) {
 
 func TestSetLabels(t *testing.T) {
 	Convey("When servicing SetLabels request", t, func() {
+		// Add feature gates as running nfd-master depends on that
+		err := features.NFDMutableFeatureGate.Add(features.DefaultNFDFeatureGates)
+		So(err, ShouldBeNil)
+
 		testNode := newTestNode()
 		// We need to populate the node with some annotations or the patching in the fake client fails
 		testNode.Labels["feature.node.kubernetes.io/foo"] = "bar"

pkg/nfd-master/nfd-master.go

@@ -801,12 +801,12 @@ func (m *nfdMaster) nfdAPIUpdateOneNode(cli k8sclient.Interface, node *corev1.No
 		// NOTE: changing the rule api to support handle multiple objects instead
 		// of merging would probably perform better with lot less data to copy.
 		features = objs[0].Spec.DeepCopy()
-		if m.config.AutoDefaultNs {
+		if !nfdfeatures.NFDFeatureGate.Enabled(nfdfeatures.DisableAutoPrefix) && m.config.AutoDefaultNs {
 			features.Labels = addNsToMapKeys(features.Labels, nfdv1alpha1.FeatureLabelNs)
 		}
 		for _, o := range objs[1:] {
 			s := o.Spec.DeepCopy()
-			if m.config.AutoDefaultNs {
+			if !nfdfeatures.NFDFeatureGate.Enabled(nfdfeatures.DisableAutoPrefix) && m.config.AutoDefaultNs {
 				s.Labels = addNsToMapKeys(s.Labels, nfdv1alpha1.FeatureLabelNs)
 			}
 			s.MergeInto(features)
@@ -864,7 +864,7 @@ func filterExtendedResource(name, value string, features *nfdv1alpha1.Features)
 }
 
 func (m *nfdMaster) refreshNodeFeatures(cli k8sclient.Interface, node *corev1.Node, labels map[string]string, features *nfdv1alpha1.Features) error {
-	if m.config.AutoDefaultNs {
+	if !nfdfeatures.NFDFeatureGate.Enabled(nfdfeatures.DisableAutoPrefix) && m.config.AutoDefaultNs {
 		labels = addNsToMapKeys(labels, nfdv1alpha1.FeatureLabelNs)
 	} else if labels == nil {
 		labels = make(map[string]string)
@@ -1041,7 +1041,7 @@ func (m *nfdMaster) processNodeFeatureRule(nodeName string, features *nfdv1alpha
 			l := ruleOut.Labels
 			e := ruleOut.ExtendedResources
 			a := ruleOut.Annotations
-			if m.config.AutoDefaultNs {
+			if !nfdfeatures.NFDFeatureGate.Enabled(nfdfeatures.DisableAutoPrefix) && m.config.AutoDefaultNs {
 				l = addNsToMapKeys(ruleOut.Labels, nfdv1alpha1.FeatureLabelNs)
 				e = addNsToMapKeys(ruleOut.ExtendedResources, nfdv1alpha1.ExtendedResourceNs)
 				a = addNsToMapKeys(ruleOut.Annotations, nfdv1alpha1.FeatureAnnotationNs)